Magnetic hysterisis is exhibited by ............ magnetic materials

Magnetic susceptibility of Mg at 300 K is $1.2 \times 10^{-5}$. What is its susceptibility at $200 \mathrm{~K} ?$

The Curie temperature of cobalt and iron are $$1400 \mathrm{~K}$$ and $$1000 \mathrm{~K}$$ respectively. At $$T=1600 \mathrm{~K}$$, the ratio of magnetic susceptibility of cobalt to that of iron is

The horizontal component of Earth's magnetic field at a place is $$3 \times 10^{-5} \mathrm{~T}$$. If the dip at that place is $$45^{\circ}$$, the resultant magnetic field at that place is